Short-term and Long-term Investments (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Apr. 30, 2014	Oct. 31, 2013
Long Term Investments
Estimated Fair Value	$ 105,091
U.S. government obligations [Member]
Long Term Investments
Amortized Cost	75,039	114,970
Gross Unrealized Gains	61	46
Gross Unrealized Losses	0	0
Estimated Fair Value	75,100	115,016
Commercial paper [Member]
Long Term Investments
Amortized Cost	29,991	24,994
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	29,991	24,994
Short-term investments [Member] | U.S. government obligations [Member]
Long Term Investments
Amortized Cost	60,042	99,974
Gross Unrealized Gains	16	11
Gross Unrealized Losses	0	0
Estimated Fair Value	60,058	99,985
Short-term investments [Member] | Commercial paper [Member]
Long Term Investments
Amortized Cost	29,991	24,994
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	29,991	24,994
Other Long-term investments [Member] | U.S. government obligations [Member]
Long Term Investments
Amortized Cost	14,997	14,996
Gross Unrealized Gains	45	35
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 15,042	$ 15,031